What are the sizes of wire?

Wire sizes in North America follow the AWG scale, where smaller numbers mean bigger wire: from fine 18 and 16 gauge cords up through 14, 12, 10, 8, 6, 4, 3, 2, and 1, then the aughts, 1/0 to 4/0, and past that kcmil sizes for big feeders.

The residential core is tight: 14 AWG for 15 amp circuits, 12 for 20, 10 for 30, 8 to 6 for ranges and subpanels, 2/0 copper or 4/0 aluminum for a 200 amp service.

By wire count, cable names add it: 12-2 means two insulated 12 gauge conductors plus ground.

Low-voltage work runs its own smaller sizes, 18 down to 22, where drop matters more than heat.

The AWG to amps calculator turns any size into its real capacity at each temperature rating.